(a) Except as provided by Subsection (b) of this section, each separate interest in minerals in place shall be listed separately from other interests in the minerals in place in the name of the owner of the interest.
(b) Separate interests in minerals in place, other than interests having a taxable value of less than $500, shall be listed jointly in the name of the operator designated with the railroad commission or the name of all owners or any combination of owners if the designated operator files with the appraisal office before May 1 a written request for joint taxation on a form furnished for that purpose. A qualification pursuant to this subsection for joint taxation remains effective in subsequent tax years and need not be requested again. However, the qualification ceases when the designated operator files a request to cancel joint taxation.